Time-limit protective device for electric circuits.



H. W. CHENEY.

TIME LIMIT PROTECTIVE DEVICE FOR ELECTRIC CIRCUITS. APPLICATION FILED MAY 27, 1997.

962,817. Patented June 28,1910.

UNITED STATES PATENT OFFICE.

HERBERT W. CHENEY, OF NORWOOD, OHIO, ASSIGNOR TO'ALLIS-CH'ALMERS COMPANY, A CORPORATION OF NEW JERSEY, AND THE BULLOCK ELECTRIC MANUFACTURING COMPANY, A CORPORATION OF OHIO.

Specification of Letters Patent; Patgnteqi J 11119 28, 1910,

Application filed May 27, 1907. Serial No. 375,830.

To all whom it may concem:

Be it known that I, HERBERT W. CHENEY, citizen of the United States, residing at Norwood, in the county of Hamilton and State of Ohio, have invented certain new and useful Improvements in Time-Limit Protective Devices for Electric Circuits, of which the following is a full, clear, and exact specification.

My invention relates to protective devices for electric circuits and especially .to time limit overload circuit-breakers.

It is often desirable that momentary overloads in an electric circuit should be permitted but that continued overloads should cause an interruption of the circuit. Circuit breakers have been provided with this end in view, and have operated with'a greater or less degree of success.

It is the object of my present invention to provide a circuit-breaker for the same purpose which shall be inore simple in principle and operation than any heretofore constructed and moreover shall be exact in its operation and easy of adjustment.

My invention comprises the combination of a body of matter which varies in volume as its temperature changes, means for causing the temperature of said body of matter to vary upon abnormal conditions in a circuit to be protected, and a circuit-breaker in said last named circuit arranged to be tripped whe the volume of said body of matter reaches a predetermined value.

. Other features of my invention will appear from the description and drawings and will be claims.

The three figures of thedrawing show diagrammatically three embodiments of my invention.

In Fi re 1 the switch 10 is closed when either 0 the solenoids 11 or 12 raises its core in response to too large a current in any branch of a three-phase circuit 1314-15. The closing of the switch 10 completes a circuit from any desired source of current 1617, through the rheostat 18v, rod 19, arm' 20 and contact 21. When the parts 20 and 21 are in, engagement, the rod 19 and said parts short-circuit a solenoid 22'. The pas sage of circuit through the rod 19, however,

- heats the latter and causes it to expand at a particularly pointed out in the trips the circuit-breaker 25 in the threephase circuit above referred to.

I Should the abnormal current in the threephase circuit not continue long enough to allow the rod 19 to expand sufliciently to break the short-circuit around the solenoid 22, the switch 10 will be allowed to open to break the circuit through said rod 19 to discontinue the heating and expansion of the latter. Thus momentary overloads are allowed while continued overloads are guarded against. The permissible duration of an overload is adjustable by the rheostat 18 while the value of the current at which the device operates is adjustable by the rheostats 26 and 27 In Fig. 2 a modification of the arrangement of circuits is shown. Here solenoid 12 closes switch 10* u on the occurrence of an excessive load on t e circuit 13 1 t. The

closing of the switch 10 completes a circuitthrough the rheostat 18*, rod 19, arm 20 and contact 21 in a manner similar to that described in connection with Fig. 1. This circuit, however, is derived from the main circuit to be protected instead of from an auxiliary source of supply as in Fig. 1.

Thus the rate at which the rod 19 expands permissible duration of the overload and oid 12 closes switch 10 upon abnormal currents in the circuit 13 -14,. The closing of the switch 10*, however, completes a circuit through a coil 30, and a rheostat 31. The coil 30 is placed around the bulb of a thermometer 32 and when vcarr in current heats the mercury orv other liquid t ereof to in Fig. 1 an auxiliary source of supply 16-17 is used, though if desired all the current may be derived from the main circuit. In

any of the modifications, a cessation of the overload allows the switch 10 or 10 to open to stop the expansion of the rod or of the mercury.

Many modifications may be made in the precise arrangements shown and described and all such which do not involve a depar ture from the spirit and scope of my inven tion I aim to cover in the claims.

What I claim as new is 1. In a protective device for-electric circuits, a body of matter which varies in volume as its temperature changes, means for causing the temperature of said body of matter to vary upon abnormal conditions in a circuit to be protected, anv electric circuit including said body of matter and arranged to have its condition as regards opening and closing reversed whenthe' volume of said body of matter reaehesQa predetermined value, and a circuit-breaker 1n the circuit to be protected'arrangd to be tripped upon such reversal.

2. In a rotective'device for electric circuits, a ho y of matter which varies in volume upon changes in tempgrature, an electric circuit for heating said dy of matter and including the latter and arranged to be completed upon abnormal conditions in a circuit to be'protected, and a circuit-breaker in said last named circuit arranged to be tripped when the volume of said'body of matter reaches a predetermined value.

3.-In an overload protective device for electric circuits, a magnetically operated switch arranged to close. when the current in a'circuit tobe protected-exceeds a predeterminedvalue, a bod of'mat-ter which expands when heated an is arranged to be electrically heated by thepassageof current through it when said switch is closed, and

a "magnetically tripped circuit-breaker in the circuitto be protected, the tripping magnet of said circuit-breaker being arranged to be energized when said body of matter has expanded to a predetermined value.

4. In combination, an electric circuit to be protected, a solenoid-operated switch arranged to be closed when more than a predetermined current flows in said circuit, a body of matter which expands on heating and which is arranged to be heated by. current supplied through said switch while the latter is closed, a circuit including said body of matter and arranged to have its condition as regards opening and closing reversed when said body of matter has expanded to a predetermined volume, a solenoid arranged to be energized upon such reversal,

and a'circuit-breaker located inthe circuit to be protected and arranged to be opened upon'the energization'of said last named solenoid. y

5. In a protective device for electric circuits, a body of matterwhich varies in volume upon changes in temperature, an electric circuit for heating said body'of matter and including the latter and arranged to be completed upon abnormal conditions in a circuit to be protected, a' circuit-breaker in said last named circuit arranged to be tripped when the volume of said body of matter reaches a predetermined value, and means for varying the rate at which said body of matter heats.

6. In combination an electric circuit to be protected, a solenoid-operated switch arranged to'be closed when more than a predeterminedcurrent flows in said circuit, a body of matter which expands on heating and which is arranged to be heated by current supplied through said switch while the latter is closed, a circuit including said body ofmatter and arranged to have its condition as regards opening and closing reversed when said body of matter has expanded to a predetermined'volume, a solenoid arranged to be energized upon such-reversal, a circuitbreaker located in the circuit to be protected and arranged to be opened upon the energization' of said lastnamed solenoid, and

means for varying the rate at which said body of matter heats.

7. In a rotective device for electric circuits, a ho y of matter which varies in volume upon changes in temperature, an electric circuit for heating said body of matter and including the latter, means for energizing said circuit upon abnormal conditions in a circuit to be protected, and a'circuit-breaker in said last named circuit arran ed. to" be trippedwhen the volumeof sai matter reaches a predetermined value In testimony whereofl afiix my signature,

in the presence of two witnemes.

HERBERT W. Witnesses? Gno. B. Sonnet, i 11- J.- KINSEY. 

